4. Lung development

Question 1

Respiratory diverticulum (lung bud)

Answer 1

4th week IUL

Outgrowth from ventral wall of foregut

Diverticulum expands caudally

Separates from foregut by two ridges - tracheoesophageal ridges

Ridge fuses to form septum - tracheoesophageal septum

Question 2

Dorsal portion of foregut

Answer 2

oesophagus

Question 3

Ventral portion of foregut

Answer 3

trachea

Question 4

Splanchnic mesoderm gives rise to

Answer 4

visceral pleura

smooth muscle

cartilage in respiratory tree

Question 5

Somatic mesoderm

Answer 5

parietal pleura

Question 6

4 periods of maturation

Answer 6

1. Pseudoglandular: 5-17 wks IUL
2. Canalicular: 16-25 wks IUL
3. Terminal sac: 24 wks IUL to birth
4. Alveolar: 29 wks IUL to 8 years old

Question 7

Pseudoglandular period

Answer 7

Branching of the respiratory tree to form terminal bronchioles Respiration NOT possible

Question 8

Canalicular Period

Answer 8

Terminal bronchioles give rise to respiratory bronchioles, which give rise to alveolar ducts

Mesodermal tissue becomes highly vascularised

Respiration is possible towards end of canalicular period

cranio-caudal differentiation

Question 9

Terminal Sac Period

Answer 9

Further terminal sacs develop

Epithelium becomes thinner

capillaries come into contact with epithelium

Endodermal epithelium differentiates to give rise to: Type I + Type II pneumocytes

Question 10

Alveolar Period

Answer 10

• Terminal sacs develop into alveolar ducts and alveolar sacs
• Expansion of the alveolar tree continues up until 8yrs

Question 11

3 Abnormalities of lung Development

Answer 11

Tracheo-Oesophageal Fistula

Lung Hypoplasia

Lung Agenesis

Question 12

Tracheoesophageal fistula

Answer 12

excess amniotic fluid

Chokes on feeding

may develop pneumonia

stomach fills with air

Question 13

Lung Hypoplasia

Answer 13

reduced number of pulmonary segments

lung is smaller

diaphragmatic hernia

Question 14

Lung agenesis

Answer 14

Lung(s) completely fail to develop

Question 15

Infant Respiratory Distress Syndrome

Answer 15

Birth at 23 wk IUL= Lack of surfactant = asphyxia

Question 16

Treating Respiratory Distress Syndrome

Answer 16

Glucocorticoid treatment accelerates foetal lung development and surfactant production

Antenatal treatment

Artificial surfactant therapy

Question 17

Answer 17

Pseudoglandular period

Question 18

Answer 18

Canalicular Period

Question 19

Answer 19

Terminal Sac Period

Question 20

Endoderm gives rise to

Answer 20

alveolar epithelium

type II pneumocytes

Question 21

Oesophageal atresia

Answer 21

polyhydramnios